Method for printing an ink jet marking on a surface

Abstract

A method for printing an ink jet marking on a non-wetting surface for liquid ink, includes forming at least a first drop of solidified ink on the surface, by ejecting, by means of a printhead, a first drop of liquid ink at a first given ejection velocity and with a first given volume, and depositing, on at least one portion of said first drop of solidified ink, at least a second drop of ink having a second volume VOL 2 , by ejecting, by means of a printhead, a second drop of liquid ink at an ejection velocity.

The invention claimed is: 
     
       1. A method for printing an inkjet marking on a surface that cannot be wetted by the ink in liquid form, that is to say a surface on which the drop of liquid ink forms a static contact angle greater than or equal to 90°, comprising the following steps:
 (a) forming at least a first drop of solidified ink E 1  on the surface, by ejecting, by means of a printhead, a first drop of liquid ink at a first given ejection velocity V 1  and with a first given volume VOL 1 , and 
 (b) depositing, on at least one portion of said first drop of solidified ink, at least a second drop of ink E 2  having a second volume VOL 2 , by ejecting, by means of a printhead, a second drop of liquid ink at an ejection velocity V 2 , 
 the first velocity V 1  being sufficient to flatten in step a) said first drop of ink on said surface and give said first drop of solidified ink E 1  a flattening contact area equivalent to the contact area obtained at equilibrium for a drop of the same liquid ink with the same volume VOL 1  present on a wettable surface, which is a surface on which the drop of liquid ink forms a static contact angle of less than or equal to 80°. 
 
     
     
       2. The printing method as claimed in  claim 1 , the first ejection velocity V 1  of the drop of ink E 1  being such that if several drops of ink E 1  having a volume VOL 1  of 6 pl are deposited at the first ejection velocity V 1 , the mean diameter of the solidified drops deposited is, seen from above, greater than 39 μm. 
     
     
       3. The printing method as claimed in  claim 1 , the surface being a surface of non-zero curvature. 
     
     
       4. The printing method as claimed in  claim 1 , the marking being printed on the surface of an optical article. 
     
     
       5. The printing method as claimed in  claim 1 , the volume VOL 1  of the drop of ink E 1  being defined such that the drop of ink E 1  is less than the critical volume for which the drop of ink E 1  bursts or rebounds when it is deposited at the first velocity V 1  on the non-wettable surface. 
     
     
       6. The printing method as claimed in  claim 1 , the surface that cannot be wetted by the ink in liquid form being such that the drops of liquid ink have a static contact angle with the surface of greater than or equal to 90°. 
     
     
       7. The printing method as claimed in  claim 1 , the drops of ink E 1  and the drops of ink E 2  respectively having a first volume VOL 1  and a second volume VOL 2  such that VOL 1 /VOL 2 <1. 
     
     
       8. The printing method as claimed in  claim 1 , the first volume VOL 1  being within the range [5 pl to 15 pl]. 
     
     
       9. The printing method as claimed in  claim 1 , the second volume VOL 2  being within the range [20 pl to 50 pl]. 
     
     
       10. The printing method as claimed in  claim 1 , said surface being a hydrophobic surface having a static contact angle with water of greater than or equal to 80°. 
     
     
       11. A method for printing an inkjet marking on a surface that cannot be wetted by said ink in liquid form, comprising a repetition of the steps of the method as claimed in  claim 1 , thus with the formation of several first drops of ink E 1  solidified on the surface and the deposition of several second drops of ink E 2  on top of said first drops E 1 . 
     
     
       12. The method for printing an inkjet marking on a surface that cannot be wetted by said ink in liquid form as claimed in  claim 11 , several of the solidified first drops of ink E 1  being formed on the surface in a first inkjet printing pass and the second drops of ink E 2  deposited on top of said first drops of ink E 1  being deposited in a second inkjet printing pass, after the first inkjet printing pass. 
     
     
       13. The method of  claim 1 , wherein the first velocity V 1  is sufficient to flatten said first drop of ink and give said first drop of solidified ink a flattening contact area equivalent to the contact area obtained at equilibrium for a drop of the same liquid ink with the same volume VOL 1  present on a surface on which the drop of liquid ink forms a static contact angle of less than or equal to 60°. 
     
     
       14. The printing method as claimed in  claim 1 , the first ejection velocity V 1  of the drop of ink E 1  being such that if several drops of ink E 1  having a volume VOL 1  of 6 pl are deposited at the first ejection velocity V 1 , the mean diameter of the solidified drops deposited is, seen from above, greater than or equal to 40 μm. 
     
     
       15. The printing method as claimed in  claim 1 , the first ejection velocity V 1  of the drop of ink E 1  being such that if several drops of ink E 1  having a volume VOL 1  of 6 pl are deposited at the first ejection velocity V 1 , the mean diameter of the solidified drops deposited is, seen from above, greater than or equal to 42 μm. 
     
     
       16. The printing method as claimed in  claim 1 , wherein the marking is printed on the surface of an ophthalmic lens. 
     
     
       17. The printing method as claimed in  claim 1 , the surface that cannot be wetted by the ink in liquid form being such that the drops of liquid ink have a static contact angle with the surface of greater than or equal to 100°.